Signal processing systems and methods

ABSTRACT

A noise reduction system for a digital receiver reduces noise in signals received at the digital receiver. The digital receiver includes an input for receiving an analogue signal, analogue signal processing circuitry for processing an analogue signal, and an output for providing the processed signal to a digital signal processor. The noise reduction system is located between the input and the analogue signal processing circuitry, and includes a first component that outputs results of a noise signal identification and a second component that applies one or more counter-measures to the received analogue signal to produce a modified analogue signal. The modified analogue signal has a reduced level of noise compared to the received analogue signal, wherein the noise reduction system is arranged to assess the effectiveness of the one or more counter-measures applied by the second component to determine whether any further counter-measures are required.

This patent application is a U.S. National Phase of International PatentApplication No. PCT/GB2018/052822 filed Oct. 3, 2018, which claimspriority to Great Britain Patent Application No. 1716120.9, thedisclosure of which being incorporated herein by reference in theirentireties.

TECHNICAL FIELD

The present invention relates to signal processing systems and methods.In particular the present invention relates to a system for processingsignals, and particularly but not exclusively to a noise reductionsystem for reducing noise in a digital receiver. Aspects of theinvention also relate to a method for reducing noise.

BACKGROUND

The reception of electronic signals is now a part of our everyday life,and we have become highly reliant upon having good reception anddecoding of data transmitted or sent through cables. The use of suchelectronic signals ranges from the prevalent use of mobile phones andother mobile electronic devices; to the use of Wi-Fi at home, in theoffice or in public areas; to broadband connections via cables andsatellite communications; as well as a whole host of unseen controlsignals for automation. An example of a control system may be foundwithin driverless vehicles which require reliable data connections totheir remote-control systems.

Unfortunately, users frequently experience difficulties when using theirelectronic devices, as the reception of a good signal capable ofsupporting specific functionality is easily affected by various issueswhich result in either a loss of signal or at least significantlyreduced bandwidth. In particular, bandwidth can significantly reducewhen the system in question encounters errors when decoding weak signals(also referred to as bit rate errors). When such bit rate errors becometoo large, the system may restrict the services available to thatapplication or user in order to preserve capacity for other users.

Large bit rate errors tend to occur when the signal-to-noise ratio (SNR)of the incoming electronic signals is low due to the presence ofinterfering noise signals within or adjacent to the signal band orchannel of the wanted signal (i.e. the modulated signal containing thedata to be decoded). Such in-band or near-band interfering noise signalscan originate from a variety of sources, both man-made andenvironmental; the noise signals can also originate from sources withsimilar applications.

For example, when considering mobile phone signal reception, interferingsignals may originate in other mobile handsets, mobile phone masts,other radio or non-radio interference sources, or simply from static orelectromagnetic interference from other electrical apparatus.Considering other application areas of electronic signals, interferingsignals can be created as a result of planet-wide interference or spaceatmospherics. Cable signals may suffer from electrical noise signals andreflected standing waves from poorly balanced signals, and signalinterference may penetrate the cable to produce electrical noise signalson the conductor carrying the wanted signal. In addition, over longdistances, both radio and cable signals will attenuate and eventuallybecome too weak to be received above the noise at the aerial and theinternal electronic noise of the amplifiers and radio receiver circuitswhere the signal is eventually received and decoded.

The present invention has been devised to mitigate or overcome at leastsome of the above-mentioned problems.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided anoise reduction system for a digital receiver for reducing noise insignals received at the digital receiver. The digital receiver comprisesan input (digital receiver input) for receiving an analogue signal,analogue signal processing circuitry for processing an analogue signal,and an output for providing the processed signal to a digital signalprocessor. It is noted that the analogue signal processing circuitry maycomprise an analogue to digital conversion such that the processedsignal provided to the digital signal processor comprises a digitalsignal. Alternatively the digital signal processor may be arranged toperform an analogue to digital conversion of the processed (analogue)signal output by the analogue processing circuitry.

The noise reduction system is located between the (digital receiver)input and the analogue signal processing circuitry, and comprises afirst component and a second component. The first component comprises aninput (first component input) arranged to receive the analogue signal; aprocessor arranged to assess the received analogue signal and toidentify one or more noise signals within the received analogue signal;and an output arranged to output the results of the noise signalidentification. The second component comprises an input (secondcomponent input) arranged to receive the results of the noise signalidentification; and electronic circuitry arranged, in dependence on theresults of the noise signal identification, to apply one or morecounter-measures to the received analogue signal to produce a modifiedanalogue signal, the modified analogue signal having a reduced level ofnoise compared to the received analogue signal. The noise reductionsystem is also arranged to assess the effectiveness of the one or morecounter-measures applied by the second component to determine whetherany further counter-measures are required. It is noted that variouselements may carry out this effectiveness assessment, depending on thedesired configuration of the overall system: for example, the(baseband/control) processor would be capable of providing thisfunctionality. Alternatively, the processor of the first component inthe noise reduction system, or even a dedicated third component with itsown processor, could carry out the effectiveness assessment.

The digital signal processor may comprise any processor arranged toprocess digital signals, e.g. a baseband processor or baseband chip or amodem. The second component may apply one or more countermeasures bygenerating one or more countermeasures in the electronic circuitry ofthe second component and then outputting (via a mixer component withinthe electronic circuitry) the generated countermeasures such that theyare mixed with the received analogue signal to produce a modifiedanalogue signal that has a reduced level of noise compared to thereceived analogue signal. The modified analogue signal may then be sentto the analogue signal processing circuitry and subsequently the digitalsignal processor.

Advantageously, the above-described noise reduction system ensures thatthe interfering noise signal is removed/reduced before it can even enterthe digital receiver's circuits and this therefore directly improves theSNR of the received signal, and removes the errors during subsequentdecoding. This enables much higher data rates and hence a givencommunications channel or cable can support higher bandwidths over muchgreater distances, resulting in improved signal reception to aparticular device. A feedback loop is also provided by the components ofthe noise reduction system, thereby enabling the system to determine thesuccess of a particular counter-measure, and whether additional oralternative counter-measures may be required. The above-described noisereduction system is therefore self-assessing and can determine whetherthe interfering noise signals have been removed, or at leastsufficiently suppressed so as to enable subsequent processing anddecoding of the wanted signal to take place.

The noise reduction system according to embodiments of the presentinvention may be used to mitigate or reduce the effects of noise signalsin a received analogue signal. Noise signals may arise from a variety ofsources and also include interfering signals within or adjacent to thesignal band or channel of the wanted signal. Noise signals that thenoise reduction system may reduce or mitigate may further comprisein-band or near-band interfering noise signals originating from avariety of sources, both man-made and environmental. Noise signals mayalso originate from sources with similar applications. When consideringmobile phone signal reception, interfering signals may originate inother mobile handsets, mobile phone masts, other radio or non-radiointerference sources, or simply from static or electromagneticinterference from other electrical apparatus. Considering otherapplication areas of electronic signals, interfering signals may becreated as a result of planet-wide interference or space atmospherics.Cable signals may suffer from electrical noise signals and reflectedstanding waves from poorly balanced signals, and signal interference maypenetrate the cable to produce electrical noise signals on the conductorcarrying the wanted signal. In addition, over long distances, both radioand cable signals will attenuate and eventually become too weak to bereceived above the noise at the aerial and the internal electronic noiseof the amplifiers and radio receiver circuits where the signal iseventually received and decoded.

In some cases, the processor of the first component may be configured toconvert the analogue signal into a digital signal, and to perform amathematical transformation on the converted digital signal, themathematical transformation identifying the one or more noise signalsand at least one property associated with each identified noise signal.

Converting the incoming analogue signal into a digital signal allows thenoise reduction system to act on a digital signal equivalent to the onethat will eventually be processed by the digital receiver itself, whilststill ensuring that the incoming signal is intercepted for noise removalprior to entering the analogue signal processing circuitry. The noisereduction system may therefore be able to identify not only the noiseinterference present in the incoming signal, but also any noise that maybe introduced into the signal by the signal processing equipment itself.Furthermore, the use of a mathematical transformation by the processorwhen identifying the noise signals enables each signal to be identifiedeasily, together with any associated properties that characterise thenoise and may help to determine the most appropriate counter-measure tobe used by the electronic circuitry of the second component to removeeach individual signal.

Optionally, the mathematical transformation comprises a Fast FourierTransform. Advantageously, the use of a Fast Fourier Transform (FFT) isa very efficient method of characterising an incoming signal as itensures that each of the noise signals (together with variouscharacterising properties of each signal) may be identified within avery short period of time (i.e. only a few instruction cycles, andpossible up to a minimum of a few picoseconds). This is particularlyuseful as it ensures that interfering signals can be identified,assessed and removed as quickly as possible, thereby allowing the noisereduction system to be adaptable and reactive to variations in theinterfering noise signals.

Optionally, the at least one property associated with each identifiednoise signal is selected from the following group: central frequency ofthe signal, signal amplitude, signal width, and signal modulation.Advantageously, characterising a particular noise signal based on itscentral frequency, and optionally also its amplitude, allows the exactlocation of the noise signal in the frequency band of interestcontaining the wanted signal (also referred to as the ‘passband’) andits size relative to the wanted signal to be determined. Identifyingthese properties makes it easier for the noise reduction system toaccurately configure any signal processing equipment to remove the noisesignal as accurately as possible, without unduly affecting the wantedsignal.

In some cases, the first component is arranged to output the results ofthe mathematical transformation via an output to an input of the secondcomponent.

Advantageously, this enables the electronic circuitry of the secondcomponent to determine the most appropriate counter measures that are tobe taken, and (if appropriate) to control its internal signal processingequipment to carry out the chosen counter measures. Alternatively, it isenvisaged that the results of the mathematical transformation areretained by the first component, and instead control signals areprovided to the second component by the processor of the firstcomponent, on the basis of these results, which instruct the electroniccircuitry of the second component to take appropriate counter measures.

In some instances, the processor of the first component may beconfigured to generate a digital matrix based on the results of themathematical transformation. Advantageously, a digital matrix provides ameans of characterising and storing identifying properties of each noisesignal using a minimum of storage space, and is therefore easy tocreate, to transmit between components and to store (where appropriate).

Optionally, the processor of the first component may be arranged toextract each of the one or more identified noise signals from theincoming/received analogue signal, and to output the extracted analoguenoise signals to the second component.

These noise signals may then be used by the noise reduction system (andparticularly the electronic circuitry of the second component) to moreaccurately remove the sources of noise, as some counter-measures mayrequire signal processing to be carried out upon the original analoguenoise signal itself. This is particularly the case for signals withcomplex profiles that cannot necessarily be characterised withsufficient accuracy based solely on properties such as central frequencyand amplitude.

In some cases, one of the counter-measures applied by the electroniccircuitry of the second component comprises configuring and applying afilter to the incoming analogue signal to remove one of the identifiednoise signals. In addition, where a mathematical transformation isperformed by the processor of the first component to identify thesignals and at least one of their properties, the applied filter may beconfigured using the at least one property.

Advantageously, the use of a pre-configured filter provides a simple andeasy way to remove a noise signal, as it minimises the amount of signalprocessing that is required to be carried out. This is particularly thecase when the identified noise signal is narrow-band, as narrow ‘notch’filters may be dynamically customised and configured using theproperties of a noise signal (for example, the notch filter may bedefined to be centred on and applied at the central frequency of thenoise signal), so as to ensure that each noise signal be accuratelyremoved without unduly affecting the wanted signal. It is noted that insome cases, the centre frequency of the notch filter may be movedslightly to avoid any accidental distortion of the wanted signal, andtherefore may not necessarily coincide exactly with the centre frequencyof the interfering signal that is to be removed. However, such offsetsshould not result in a detrimental effect on the efficacy of the noiseremoval.

In some instances, the electronic circuitry of the second component isconfigured to generate a replica noise signal corresponding to one ofthe identified noise signals. The electronic circuitry of the secondcomponent may also adjust the replica noise signal so that it issubstantially in anti-phase with the identified noise signal, and thenmix the adjusted replica noise signal with the incoming analogue signal.

In cases where the identified noise signals will not be so easilyremoved using a simple notch filter (for example, in the case ofwide-band noise), a simple method of removing such noise signals may beto generate a replica signal, using the electronic circuitry of thesecond component, that mimics the properties and profile of eachidentified noise signal. This replica signal may then be inverted andphase-adjusted, such that it is in anti-phase with the correspondingnoise signal. Mixing this processed/adjusted replica signal with theincoming analogue signal should ensure that substantially all of thenoise signal in question is cancelled out, or at least reduced to anacceptable level within the modified analogue signal.

Optionally, the replica noise signal may be generated, using theelectronic circuitry of the second component, based on the generation ofa tonal signal. Additionally or alternatively, the replica noise signalmay be generated based on the extracted noise signals received from thefirst component.

Where the identified noise signal corresponds to a fairly simple signal,the noise reduction system (and specifically the electronic circuitry ofthe second component) may generate a tonal (or sine-wave) signal,usually of the same frequency as that associated with the identifiednoise signal, to form the basis of the replica noise signal. This methodis useful as it merely requires relatively simple, standard signalprocessing equipment, in combination with knowledge of one or more keyproperties of the noise signal in question. Alternatively oradditionally, where the identified noise signal is more complex andcannot be represented accurately by a simple tonal signal, theelectronic circuitry of the second component may use the actual noisesignals extracted from the incoming analogue signal by the processor ofthe first component, to form the basis of the generated replica noisesignal.

In some scenarios, the processor of the first component may be arrangedto generate and output a control signal to the input of the secondcomponent to control the counter-measures that are applied by theelectronic circuitry of the second component. This is useful as thefirst component carried out the identification of the noise signals, andtherefore it would be efficient for the first component to also be ableto specify how the electronic circuitry of the second component is toremove/reduce the noise signals.

In some cases, the processor of the first component may be arranged toassess the effectiveness of the one or more counter-measures applied bythe electronic circuitry of the second component. Alternatively, theprocessor of the first component may be arranged to output a controlsignal to a third component to control an effectiveness assessment whichis carried out by (a processor of) the third component.

Optionally, at least one of the first and second components is arrangedto be controlled via output of a control signal from the digital signalprocessor to the respective component. If applicable, the thirdcomponent may also be arranged to be controlled via output of a controlsignal from the digital signal processor to the respective component.

It may be advantageous for the processor of the first component to carryout the assessment of the effectiveness of the noise reduction system,as it is already set up to analyse the incoming analogue signal toidentify sources of noise. Alternatively, the processor of the firstcomponent may control another (third) component to carry out theassessment on its own. Furthermore, it may be advantageous for theoverall functionality of the noise reduction system to be controlled bya single entity or component for simplicity and efficiency, where thatsingle controlling component is provided with the majority of theprocessing and storage capability, and the other components effectivelyfunction as subsidiaries and receive control signals from thecontrolling component to carry out their individual functions. In somecases, the controlling component may correspond to the (processor ofthe) first component, or to a separate processor, such as the digitalsignal processor of the digital receiver, which is already incorporatedwithin the digital receiver.

In some instances, the third component may be arranged, once theelectronic circuitry of the second component has applied the one or morecounter-measures to the incoming analogue signal to form the modifiedsignal, to assess the modified analogue signal using a processor, and toidentify one or more residual noise signals in the modified analoguesignal.

By effectively diverting or ‘tapping off’ a portion of the analoguesignal for assessment, the third component is able to identify anyresidual noise signals that still remain within the analogue signal, thepresence of which would indicate that the counter-measures applied bythe second component were not (entirely) successful. The third componenttherefore provides a means of assessing the performance of the noisereduction system substantially in real-time to determine whether anyadditional or alternative counter-measures need to be carried out; orwhether the counter-measures have reduced the noise to an acceptablelevel for signal decoding to be carried out successfully.

Specifically, a processor of the third component may be arranged tocarry out a mathematical transformation of the modified analogue signal(i.e. the received analogue signal after the one or morecounter-measures have been applied by the electronic circuitry of thesecond component), for comparison with the mathematical transformationcarried out by the processor of the first component on the receivedanalogue signal. This will enable a direct ‘before’ and ‘after’comparison to be made, and will allow the characterising properties ofthe residual noise to be determined. This will, in turn, influence thesubsequent counter-measures that are applied by the electronic circuitryof the second component.

It will be appreciated that the processor of the first component maycarry out the effectiveness assessment in the above-described manner, inwhich case, no dedicated third component would be required, and all ofthe features described above would apply equally to the first component.

In some cases, the digital receiver comprises or corresponds to adigital receiver in a mobile device. In this case, the input comprises amobile device aerial and the digital signal processor comprises abaseband processor of the mobile device.

Where the above-described noise reduction system is implemented in thecontext of a mobile device (for example a mobile phone), it canadvantageously increase the signal strength perceived by the mobiledevice digital receiver due to a reduction in bit rate errors. In turn,this may also extend the battery life of the mobile device, since thepower to the RF sections of the mobile device can be reduced as thereceived signal strength increases.

The incoming/received analogue signal may comprise any one of thefollowing: mobile network signals, radio signals, Wi-Fi signals,satellite communications, broadband connections. The applications of thepresent noise reduction system are diverse, and can be used to increasesignal strength and coverage over a variety of different technologicalfields. For example, it is envisioned that the system described above(or the method that is described below) could be implemented in a radioreceiver which is arranged to receive a signal containing interference,so as to attenuate, reduce or remove the interference in the signal.

According to another aspect of the present invention, there is provideda noise reduction method for reducing noise in signals received at adigital receiver, the digital receiver comprising an input (digitalreceiver input) for receiving an analogue signal, analogue signalprocessing circuitry for processing an analogue signal, and an outputfor providing the processed signal to a digital signal processor,wherein the method comprises: assessing, by a processor of a firstcomponent located between the input and the analogue signal processingcircuitry, the received analogue signal and identifying one or morenoise signals within the analogue signal; applying, by electroniccircuitry of a second component located between the input and theanalogue signal processing circuitry, one or more counter-measures tothe received analogue signal in dependence on the identified noisesignals in order to produce a modified analogue signal, the modifiedanalogue signal having a reduced level of noise compared to the receivedanalogue signal; and assessing the effectiveness of the one or moreapplied counter-measures to determine whether any furthercounter-measures are required.

According to another aspect of the present invention, there is provideda computer program product comprising instructions which, when theprogram is executed by a computer, cause the computer to carry out thesteps of the above-described method.

According to a further aspect of the present invention, there isprovided a computer-readable storage medium comprising instructionswhich, when executed by a computer, cause the computer to carry out thesteps of the above-described method.

According to a further aspect of the present invention, there isprovided a mobile device comprising a noise reduction system, orcarrying out the noise reduction method, as described above. This mobiledevice may comprise a mobile phone or other similar device.Alternatively, a WiFi router or similar device may be providedcomprising the noise reduction system or carrying out the noisereduction method discussed above.

Within the scope of this application it is expressly intended that thevarious aspects, embodiments, examples and alternatives set out in thepreceding paragraphs, in the claims and/or in the following descriptionand drawings, and in particular the individual features thereof, may betaken independently or in any combination. That is, all embodimentsand/or features of any embodiment can be combined in any way and/orcombination, unless such features are incompatible. The applicantreserves the right to change any originally filed claim or file any newclaim accordingly, including the right to amend any originally filedclaim to depend from and/or incorporate any feature of any other claimalthough not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by wayof example only, with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a typical digital receiver utilised forprocessing electronic signals in a mobile phone handset;

FIG. 2 is a schematic block diagram showing components of a noisereduction system for reducing noise in a digital receiver, according toan embodiment of the present invention;

FIG. 3 is a schematic block diagram showing a more detailed illustrationof the components of the noise reduction system of FIG. 2, where thenoise reduction system is incorporated into a typical mobile phonesystem architecture;

FIG. 4 is a schematic block diagram showing further details of a firstcomponent of the noise reduction system of FIG. 2 for assessing theincoming signal and identifying sources of noise;

FIG. 5 is a schematic block diagram showing a first portion of a secondcomponent of the noise reduction system of FIG. 2 for applyingcounter-measures to remove the identified noise in the received signal;

FIG. 6 is a schematic block diagram showing a second portion of thesecond component of the noise reduction system of FIG. 2;

FIG. 7 is a flowchart showing the general method utilised by the noisereduction system of FIG. 2 to reduce the noise in a digital receiver;and

FIG. 8 shows a series of diagrams illustrating the effects on anelectronic signal when noise reduction is carried out by the noisereduction system of FIG. 2.

DETAILED DESCRIPTION

Although the majority of this specification focuses on theimplementation of a noise reduction system in a typical mobile phonehandset, it should be understood that possible applications of such asystem cover various other forms of devices, and also involve a widerange of technologies and fields. As long as signal transmission andreception occurs in a system, regardless of the medium, the noisereduction system described herein will be of benefit. For example, thenoise reduction system may be used in the context of mobile networks,radio communications, Wi-Fi, satellite communications, or even broadbandcable connections (either copper cable or fibre optic cables).

In order to place the invention in context, a description will now beprovided of the existing digital receiver architecture that is providedwithin a typical mobile phone for converting incoming analogue signalsinto digital signals that are subsequently processed and decoded. Itwill be appreciated however, that such a mobile phone digital receiversystem and how it works will be known to the skilled person, andtherefore only a very brief summary will be provided here.

FIG. 1 illustrates the configuration and components of a typical mobilephone or other equivalent mobile device, which commonly employssoftware-defined radio (SDR) techniques. The mobile device comprises anaerial or antenna 2 for receiving the incoming analogue signals, andanalogue signal processing circuitry 4 for carrying out initial signalprocessing of the incoming analogue signal into an analogue basebandsignal that can then be converted into a digital signal. The analoguesignal processing circuitry can be seen to operate on the receivedmodulated analogue signal to retrieve the modulated portion of thereceived analogue signal in the form of an analogue baseband signal.

The mobile device also comprises a processor 6 (generally referred to asa digital baseband processor) which carries out further processing anddecoding of the resultant digital signal. In greater detail, theincoming signal creates a voltage on the aerial 2 which is passedthrough several bandpass filters 8 and amplifiers (not shown) within theanalogue signal processing circuitry 4, and then is mixed using a mixer10 to produce I and Q signals at the baseband frequency. These analoguebaseband signals are then passed through further filters and amplifiers12 before being digitized by ADC (Analogue-digital-converter) functions14; the resultant digital signal is then passed to the digital basebandprocessor 6 for decoding. In the illustrated case, it is noted that theanalogue signal processing circuitry 4 is configured to carry out theconversion of the incoming analogue signal into a digital signal.However, it should be appreciated that this may not always be the case,and that in some cases, only a subset of analogue signal processing maybe carried out by the analogue signal processing circuitry 4, with theanalogue-to-digital conversion process instead being performed byanother component subsequently, for example by the baseband processor 6.

The amplifiers 12, regardless of whether they are hardware- orsoftware-controlled, are configured to try to ensure that the wantedsignal amplification is near to the available full scale of the system,so as to achieve maximum SNR. However, if signals from other sources arepresent within the bandwidth of the wanted signal, then theamplification is restricted to ensure that these amplified noise signalsdo not exceed the system's capabilities or full scale. Such a situationmay be referred to as overload. From tests performed on typical 4G LTEMobile receivers, it is noted that the wanted signal suffers significantdegradation due to these adjacent signals, which is of course,undesirable.

FIG. 2 provides a high-level illustration of a noise reduction system20, according to an embodiment of the present invention, that may beincorporated into existing mobile phone systems.

The noise reduction system 20 of this embodiment is integrated into theexisting mobile phone system architecture, and is designed to act on theincoming analogue signals 21 before they are processed by the analoguesignal processing circuitry 4 and then converted into digital signals.

The noise reduction system 20 comprises three components or functionalblocks which each carry out a different type of task. A first ‘signalassessment’ component 22 is configured to analyse or assess the receivedanalogue signal 21 and to identify the various sources of noise presentwithin the received signal; and a second ‘counter-measure application’component 24 is configured to use various electronic circuitry elements(for example, filters, mixers, amplifiers, switches etc.) to take one ormore of a plurality of counter-measures in order to reduce or eliminatethe identified sources of noise. This may involve incorporatingadditional signals into the incoming analogue signal via a mixer 25 suchthat a “modified analogue signal” 23 is passed to the analogueprocessing circuitry 4. A third ‘performance assessment’ component 26 isconfigured to assess the performance of the noise reduction system 20 byanalysing the modified analogue signal 23 (in other words analysing thereceived analogue signal after it has been acted upon by the secondcomponent 24), and identifying sources of noise still present within theanalogue signal in order to ascertain whether any further or additionalcounter-measures need to be taken by the second component 24.

In addition to carrying out the initial noise level assessment of theincoming signal, in this embodiment, the first component 22 is alsoarranged to have overall control over the functioning of the noisereduction system 20 as a whole. In particular, the first component 22 isarranged to control the types of counter-measures that are taken by thesecond component 24, as well as to control the manner in which the thirdcomponent 26 assesses the overall noise reduction system 20 performance.However, it will be appreciated that this setup is merely one of severalpossible configurations—for example, other components such as thebaseband processor 6 may have control over all or part of the noisereduction system 20.

As a result of its location within the existing mobile phone systemarchitecture and configuration, the noise reduction system 20 is able toremove or mitigate the interfering noise signals from the incomingsignal before it enters the analogue signal processing circuitry 4. Thisdirectly improves the SNR of the analogue signal that is processed anddigitised, and removes or reduces errors in the subsequent decoding ofthe digital signals. This enables much higher data rates to be achieved(due to the reduction in errors) and hence a given communicationschannel can support higher bandwidths over much greater distances.

It is noted that the received analogue signal is a signal that comprisesthe wanted signal (i.e. the modulated analogue signal that contains thedata to be decoded) and noisy/interfering signals. It can be seentherefore that the noise reduction system according to embodiments ofthe present invention operates to receive the incoming analogue signaland then to reduce or mitigate the effects of noise within the receivedanalogue signal in order to output a modified analogue signal thatcomprises the wanted signal and fewer noisy/interfering signals(compared to the received analogue signal). This modified analoguesignal is then passed to the analogue processing circuitry whichoperates as described in relation to FIG. 1 to retrieve the modulatedportion of the modified analogue signal in the form of an analoguebaseband signal.

FIG. 3 shows in greater detail the configuration of the noise reductionsystem 20 that was broadly described in FIG. 2. In particular, FIG. 3shows the location of the various components of the noise reductionsystem relative to the existing receiver architecture (as shown inFIG. 1) and the existing signal processing paths.

The first ‘signal assessment’ component 22 of the noise reduction system20 is arranged and functions effectively parallel to the analogue signalprocessing circuitry 4 in terms of signal processing. In other words,the first component 22 (which is also referred to as Function A in thefigure) is arranged to also receive the incoming analogue signal 21 fromthe aerial 2 and to process and digitise (if applicable) this analoguesignal in a similar manner as the existing analogue signal processingcircuitry 4. The first component 22 is configured to provide two outputs30, 32 to the second component 24 in order to allow various noisereduction counter-measures to be taken subsequently—a first output 30comprising information characterising each source of noise identified bythe first component 22 to be present within the signal; and a secondoutput 32 comprising the actual identified noise signals.

In the illustrated embodiment, the second ‘counter-measure application’component 24 of the noise reduction system 20 actually comprises twosub-components 34, 36 (labelled in the figure as Functions B and C),which are arranged to apply various noise reduction/removalcounter-measures to the incoming analogue signal (using the variouselectronic circuitry elements incorporated in each sub-component) suchthat a modified analogue signal 23 enters the analogue signal processingcircuitry 4. Specific examples of such counter-measures will bediscussed subsequently with reference to FIGS. 5 and 6, however ingeneral, there are two different categories of counter-measures that areusually applied, depending on the properties of the noisesignal—typically wide-band and narrow-band noise signals will requiredifferent treatment. One category of counter-measures involves theactive filtering and removal of signals (usually very narrow-bandsignals), whilst the other category involves the generation of replicanoise signals which are then inverted and mixed into the incominganalogue signal. This latter method has the effect of ‘cancelling out’the noise signals in the incoming analogue signal before the signalreaches the analogue signal processing circuitry 4.

It will be appreciated that although two separate sub-components 34, 36are shown in this figure, their functionality could be incorporated intoa single component—i.e. Functions B and C could be combined into asingle functional block if so desired.

It is noted that in FIG. 3, the first component 22 is shown as beingconfigured to control the second component 24—connections betweenFunction A and Functions B and C are shown in the figure. As mentionedpreviously however, these connections need not necessarily be in placefor the system 20 to function. Alternative embodiments are envisioned inwhich the main controlling entity is the baseband processor 6, oranother separate processing component.

Finally, the third ‘performance assessment’ component 26 of the noisereduction system 20 (which is labelled as new Monitor (A) in the figure)is arranged to receive the modified analogue signal before it enters theanalogue signal processing circuitry 4, but after the output from thesecond component 24 (i.e. after the appropriate counter-measures havebeen applied to the incoming analogue signal). The third component 26 istherefore able to directly evaluate the performance of the noisereduction system and provide feedback on the success of the variouscounter-measures that have been applied.

It will be appreciated that due to its similarity to the first component22, the third component 26 may be a subsidiary of the first component22, and/or directly controlled by the first component 22.

Alternatively, the third component 26 may be incorporated into theexisting mobile phone system architecture and its functionality mayinstead be carried out by the baseband processor 6.

A more detailed description of each of the three components will now beprovided with reference to FIGS. 4 to 6.

FIG. 4 shows a schematic diagram of the first component 22, forassessing the incoming analogue signal 21 and identifying sources ofnoise (and therefore also referred to interchangeably herein as the‘signal assessment’ component), from which it can be seen that thepre-processing and analogue-to-digital conversion (ADC) functionality ofthe analogue signal processing circuitry is effectively replicatedwithin the first component.

In particular, the first component 22 comprises an input 38 forreceiving the incoming analogue signal from the aerial 2; as well as aset of pre-processing equipment—namely, a series of bandpass filters 8,amplifiers 12 (for example, LNAs, or Low Noise Amplifiers) and mixers10—which replicates the existing analogue signal processing circuitry 4.It will be appreciated that the pre-processing equipment provided in thefirst component 22 may be optional, as instead of selecting a specific(desired) frequency band containing the wanted signal, the firstcomponent 22 could instead operate on, and forward to the secondcomponent 24, the entire received analogue signal. The first component22 also comprises an ADC function 14 (Analogue-to-Digital Converter)similar to that provided in the existing analogue signal processingcircuitry 4 for generating a digital signal. The first component 22 istherefore able to perform simple band filtering and obtain a similarpre-processed analogue signal to that which is produced in the existingmobile phone analogue signal processing circuitry 4. The first component22 also comprises a pair of outputs 40, 42 for providing data andsignals to the other components 24, 26 in the noise reduction system 20,as well as a processor 44 for controlling the noise characterisationprocesses, and for handling interactions with the other components 24,26 in the noise reduction system 20.

The processor 44 of the first component 22 is programmed withinstructions to assess the digital signal generated by the ADC 14 and toidentify the interfering noise signals that are present in the digitalsignal. In particular, the processor 44 is configured to carry out aFast Fourier Transform (Fast FFT) 46 on the digital signal in order toidentify each individual component that is present within the receivedsignal (i.e. both wanted signal as well as the various interfering noisesignals), and to determine various properties associated with eachsignal component. A digital matrix 48 is output via the first output 40as a result of the FFT 46 which contains, for each identifiedinterfering noise signal, its central frequency and amplitude withrespect to the wanted signal (although other signal properties may alsobe included). Since the properties of the wanted signal (for example,the central frequency) are known, the wanted signal component may beidentified within the FFT results and excluded from the digital matrix.On the basis of this FFT result, the processor 44 is also configured toextract one or more of the identified noise signals 32 from thepre-processed analogue signal (prior to its digitisation by the ADC) ifit is deemed appropriate to do so; this signal extraction is achievedvia the use of a software-controlled switch 50 and one or moreprogrammable band-pass filters (not shown). The generated digital matrix48 and the extracted noise signals 32 (if the latter are required) arethen output via the second output 42 from the first component 22 to thesecond component 24 to allow various counter-measures to be applied tothe incoming signal.

An advantage of using a Fast Fourier Transform to characterise the noisein the incoming signal is that the process used to compute the Fast FFT46 takes only a few instruction cycles and can be performed in real-timeusing the current hardware available in a typical baseband processor 6of a mobile phone handset, or a dedicated processor or ASIC(Application-specific Integrated circuit). However, it will beappreciated that other mathematical transformations that achieve similarresults in comparable time periods could also be used here. For example,various well-known spectrum estimation techniques or methods ofestimating power/frequency distribution may be utilised instead of, orin addition to the FFT.

It should also be noted that the extraction of the noise signals may becarried out by either (a) using one or more programmable band passfilters to ‘pass out’ or extract each noise signal from the analoguesignal; or (b) by removing the ‘wanted signal’ from the analogue signal(using a programmable notch filer) and then subsequently outputting theremaining portions of the signal. It will also be understood that as thefirst component 22 is carrying out the initial characterisation of thenoise in the incoming signal, this component 22 is therefore well-placedto control the subsequent noise removal and performance assessmentprocesses that are carried out by the other two components 24, 26 as thefirst component 22 will be aware of the actions that need to be taken inorder to ensure optimal noise reduction. However, control of the othercomponents 24, 26 in the noise reduction system 20 could instead becarried out in an alternative manner, for example by a separateprocessor 6 that may be part of the existing mobile phone architecture.

Turning now to the second component 24 of the noise reduction system 20,for applying one or more counter-measures to remove noise from thesignal (and therefore also referred to interchangeably herein as the‘counter-measure application’ component), it will be appreciated thatthere are many different sources of noise which results in theidentified interfering noise signals having a wide range of properties;certain counter-measures will therefore be particularly effective atreducing or eliminating noise signals with specific properties. Examplesof various functional blocks or sub-units that could be incorporatedinto the second component 24 in order to carry out variouscounter-measures will now be described with reference to FIGS. 5 and 6.

FIG. 5 illustrates the internal configuration and electronic circuitryof the first sub-component 34 (labelled as Function B in FIG. 3) of the‘counter-measure application’ component 24 which is configured toprovide the requisite functionality to remove relatively simple noisesignals, which are suitable to be inverted and mixed into the incominganalogue signal (to form the modified analogue signal that is passed tothe analogue signal processing circuitry 4).

As shown in the figure, the first sub-component 34 comprises two inputs52, 54 which each correspond to a separate signal processing andgeneration path; the first sub-component 34 also comprises a third‘control’ input 56 whereby control signals from the ‘signal assessment’component 22 are received and used to control the signal processingequipment in the first sub-component 34. The first input 52 is arrangedto receive the digital matrix 48 of signals from the first component 22,and the signal processing equipment and electronic circuitry providedalong the corresponding path comprises a DAC 58 (Digital-to-AnalogueConverter) and a VCO 60 (Voltage-Controlled Oscillator). This firstsignal processing path involves using the received digital matrix 48 togenerate a replica of one or more noise signals by using the DAC 58 toproduce a voltage to control the VCO 60, which in turn creates a signalof the required frequency (i.e. a signal centred on the frequencycorresponding to that of the interfering noise signal in question). Thissignal is then shaped and phase adjusted using various electroniccircuitry elements such as filters, adaptive LMS (Least Mean Square)circuits and LNA RF amplifiers (collectively labelled as 62) to producea substantially equivalent adjusted replica of the interfering signal.Signals that may be usefully replicated by this technique are thosewhich are relatively simple—for example simple noise spikes, as well assimple single tones or predominantly tonal interfering signals.

The second input 54 and signal processing path is arranged to receiveand transmit the noise signals 32 that were extracted from the incominganalogue signal by the first component 22. This second signal processingpath is generally utilised for those noise signals which have morecomplex profiles and would therefore be much more difficult to replicateusing the first signal processing path described previously, for examplegeneral background noise levels in the signal may require utilisation ofthe counter-measure provided by the second signal processing path. Itwill be appreciated that depending on the level of noise present in theoriginal incoming analogue signal, as well as the types of noise thatare present, this second path need not always be utilised. For example,if only simple easily-replicable signals are present in the incominganalogue signal, then this second path will not be required. Theoptional nature of this second path is represented in the figure by aswitch 64, which may be controlled by the first component 22 to ‘open’the second path if appropriate, for example if it is determined (by thethird component 26) that the background or overall level of noise in theincoming signal is still not at a sufficiently low level.

The first sub-component 34 also comprises a mixer 66 to combine thereplica noise signals that are generated along the first signalprocessing path, with the analogue signals received from the firstcomponent 22 that are transmitted along the second signal processingpath, into a single signal. The resultant combined replica signal issubsequently acted upon by the various inverters and phase adjusters 62which ‘shape’ the combined replica signal into an adjusted replicasignal having a form that can be used to cancel out the noise signalsthat have been determined to be present in the original incominganalogue signal. This signal processing equipment, in this embodiment,is also controlled by the first component 22 via the third ‘control’input 56.

The adjusted replica noise signal is then output to the secondsub-component 36, where further adjustments are applied (if necessary)in order to match the adjusted replica noise signal as closely aspossible to the incoming interfering noise. In particular, as can beseen from FIG. 6, the second sub-component 36 (labelled Function C inFIG. 3) of the ‘counter-measure application’ component comprises variouselements of electronic circuitry, including fine phase adjusters 70, aswell as multi-tap delay lines 72 a, b. The fine phase adjusters 70 areused to adjust the phase of narrow-band noise signals (for examplerelatively narrow noise spikes), as the phase of these signals does notchange over the frequency span of the signal. The delay lines 72 a, bare used to apply the appropriate delay to wide-band signals for whichthe delay cannot be produced by simple phase-shifting since the phase ofthe signal will change over the frequency span of the signal. The secondsub-component 36 also comprises one or more amplifiers (e.g. LNAs) 74that are used to adjust the amplitude of the adjusted replica signals tomatch the amplitude of the incoming interfering noise signals. As withthe first sub-component 34, the signal processing equipment in thesecond sub-component 36 may also be controlled by the first component22, or alternatively by another separate component such as the basebandprocessor 6. A switch 76 is also provided, as well as a mixer 78 (it isnoted that mixer 78 of FIG. 6 carries out the same function as mixer 25of FIG. 2), to control the addition of the adjusted replica noisesignals to the incoming analogue signal to form the modified analoguesignal 23 that is passed to the analogue signal processing circuitry 4.

The second sub-component 36 further comprises one or more configurablesignal filtering electronic circuitry components that are arranged toremove or cut out specifically-identified noise signals from theincoming analogue signal. Specifically, the second sub-componentcomprises one or more programmable narrow-band notch filters 80, whichare configured using the digital matrix 48 of noise signals generated bythe first component 22. These narrow band notch filters 80 are definedto have a centre frequency matching that of each identified noise signalthat is to be cut out, and are usually used in situations where theinterfering signal is deemed not to be suitable to be inverted and addedinto the incoming analogue signal. Such narrow band notch filters 80have a much sharper performance over a narrow frequency band thanexisting wideband filters, thereby enabling the removal of interferencewithout unduly affecting the shape or characteristics of the wantedwideband signal.

The second sub-component 36 also comprises a multi-tap delay line 72 bwhere delays are applied to the incoming analogue signal where phasematching is required prior to mixing in the signals, generated by thefirst sub-component 34, using the mixer 78. This is only used where thephase match cannot be achieved from the first sub-component 24.

It will be appreciated that the nature of the interference signals maybe such as to require constant adjustment of the filters 80 inreal-time, for example where the sources and/or the level of noisevaries rapidly over time. However, by using a third component 26 whichassesses the performance of the noise reduction system 20 (by monitoringthe modified analogue signal) and provides feedback to one or more ofthe other components 22, 24, the filtering process carried out by thenotch filters 80 is dynamic and adaptive, and allows the system 20 toactively react to and compensate for variations in noise. In addition,as the results of the filtering and signal removal are monitored by thethird component 26, once it is determined that the residual noise is ata suitable level to enable the digitised signal to be decoded fullywithout errors, the noise reduction process (for that particular signalor set of signals) can be considered to be complete and no furtherchanges made until the incoming interference changes.

The present invention uses the ability of narrow bandwidth filters 80 toprovide a much more controlled frequency range and bandwidth fortargeted noise removal than existing band filters found in currentmobile phone digital receivers. This is because existing band filtershave a wide passband required for high bandwidth signals creating amuch-reduced performance in terms of the ability to remove near-band orin-band interfering noise signals.

An example of a method 100 used by the noise reduction system 20according to an embodiment of the present invention will now bedescribed with reference to FIG. 7, and the effects of such a method areillustrated in FIG. 8.

The method 100 begins in Step 105 with receipt of the incoming analoguesignal from the aerial 2 by the first (‘signal assessment’) component 22in the noise reduction system 20. The first component 22 comprises aduplicate set of band filters and other pre-processing equipment 8, 10,12, 14 that are present in the existing analogue signal processingcircuitry 4, and is programmed with data regarding the wanted signal—forexample, the channel (frequency) of the wanted signal is known from thebaseband processor. The first component 22 is therefore able to carryout pre-processing and digitisation of the analogue signal in Step 110to generate an equivalent digital signal to that which would be producedby the mobile phone analogue signal processing circuitry 4. The firstcomponent 22 is then configured to carry out a rapid FFT 46 in Step 115on the digitised signal (which will require only a few clock cycles oftime or instruction cycles—for example, up to a minimum of a fewpicoseconds) in order to identify all of the individual components thatare comprised in the signal—this includes both the wanted signal as wellas all other interfering noise signals that are also present within thepassband of the filters. Such interfering noise signals may have centrefrequencies that are out of the band of interest for the wanted signal,but the signal spectrum may still encroach on the passband of the wantedsignal. In this case, the FFT will merely flag (side lobe) frequenciesof the noise which encroach on the frequency band of interest. A digitalmatrix 48 of all of the identified interfering noise signals is createdby the first component 22, where each signal is characterised by itsassociated frequency and size (i.e. amplitude); optionally, othercharacteristics of the signals such as their width (i.e. spectrumspread) and modulation may also be included in the generated matrix.Based on this identification of all the interfering noise signals, thefirst component 22 configures a set of passband filters of appropriatewidth and frequency to extract in Step 120 each of the interfering noisesignals from the received analogue signal.

The digital matrix 48 that characterises each of the signals, togetherwith the extracted noise signals 32 if appropriate, are then transmittedin Step 125 to the second (‘counter-measure application’) component 24,where the most appropriate noise removal technique is applied for eachof the identified noise signals. In some instances, the first component22 determines the most appropriate noise removal counter-measure to betaken, as the necessary information is contained within the digitalmatrix 48 generated by the first component 22 during the FFT 46;however, in some instances, the second component 24 may carry out thedetermination based on the digital matrix 48 received from the firstcomponent 22. The exact implementation method that is utilised willdepend on the device and system in which the noise reduction system 20is used (and may, for example, depend on the spare processing capacity).Alternatively, all or part of the noise reduction system 20 may becontrolled by the baseband processor 6.

For signals having a single narrow frequency, the second(‘counter-measure application’) component 24 will first attempt toremove in Step 130 the signal via the generation of a replica signal bythe first sub-component 34 (corresponding to Function B in the figures)using its internal electronic circuitry. This is carried out via thefirst signal processing path that was previously described withreference to FIG. 5. Specifically, the first sub-component 34 of the‘counter-measure application’ component may generate a sine wave typesignal (also sometimes referred to as a tonal signal) of the samefrequency as the noise signal in question. As previously described, theDAC 58 and VCO 60 combination in that sub-component 34 perform thisfunction based on the information obtained from the digital matrix 48,and optionally under the control of the first component 22. Additionallyor alternatively, for signals that are more complex, the firstsub-component 34 may utilise in Step 135 the second signal processingpath to produce a replica signal based on the analogue noise signals 32that were received from the first component 22. As was discussedpreviously, the signals produced by the two signal processing paths maythen be mixed to produce a combined replica signal. The resultantreplica signal will then be passed through an adaptive LMS filter andfine phase adjuster 62 to create an adjusted replica signal that issubstantially in anti-phase with the originally-identified interferingsignal. This adjusted replica signal is then mixed in Step 140 with the‘live spectrum’—i.e. the incoming analogue signal by the secondsub-component 36 to form a modified analogue signal 23—before it entersthe existing analogue signal processing circuitry 4. As notedpreviously, the second sub-component 36 may apply further adjustments tothe adjusted replica signal if necessary in order to bring the signalcloser into anti-phase with the incoming signal.

The third component 26, which comprises almost identical circuitry tothe first component 22, constantly monitors the modified analogue signal23 immediately after output from the second component, and is able toestablish in Step 145 in real-time if the technique that has beenapplied has resulted in the interfering signal being successfullycancelled out, or reduced to an acceptable level. Specifically, thethird component 26 is effectively a duplicate of the first component 22,and also acts under the control of the first component 22; the thirdcomponent 26 therefore also digitises the input signal (comprising amixture of the original signal and the generated adjusted replicasignal) and performs a Fast FFT 46 of the digitised signal to generate adigital matrix 48 of the noise present in the modified analogue signal23. The FFTs from the first 22 and third 26 components can then becompared to determine whether the signal(s) in question have beenremoved adequately. Alternatively, an analysis of the FFT result fromthe third component 26 could be carried out on its own to identify thepresence of residual noise signals.

If some residual interference from these signals is still determined tobe present in the modified analogue signal 23, then the next techniqueis applied in Step 150, namely to dynamically configure and apply a verynarrow notch filter 80 at the centre frequency of each interferingsignal that is to be removed. This technique is carried out by thesecond sub-component 36. The centre frequency of the notch filter 80 canbe moved to avoid any accidental distortion of the wanted signal, andtherefore may not necessarily coincide exactly with the centre frequencyof the interfering signal that is to be removed. However, such offsetsshould not result in a detrimental effect on the efficacy of the noiseremoval.

For wide signals with complex modulation, the process of generating areplica signal based on a simple tonal signal may not be appropriate. Insuch cases, the signal characteristics contained within the digitalmatrix 48 produced by the first component 22 are used by the secondcomponent 24 to define filter characteristics of one or moreconfigurable notch filters 80 that will be used to perform removal ofthe interfering signal. As discussed above, the centre frequency of thenotch filter may potentially be slightly offset from the centrefrequency of the interfering signal to avoid any accidental distortionof the wanted signal during removal of the interfering signal.

As with the previously-described technique for narrow signals, the thirdcomponent 26 will monitor in Step 155 the modified incoming analoguesignal 23 in order to ascertain whether the noise removal techniqueshave been applied correctly and the extent of their success. Thisfeedback and monitoring process enables the noise removal techniques tobe altered in real-time so as to provide optimum and targeted noisereduction.

For general in-band noise, a combination of both the above techniqueswill generally be utilised, although it will be appreciated that thenoise removal techniques described herein can be applied in differentorders, or even at the same time. For example, in some instances, it maybe preferable for the notch filter signal removal technique to beapplied first, followed by the signal replication removal technique toremove any residual noise signals

In one embodiment, it is envisioned that the notch filters 80 will firstbe tuned to remove all noise signals except the spectrum of the wantedsignal (for example, in some cases this can remove up to 90% of theinterfering signals); the remaining noise is subsequently reduced bymixing an antiphase-adjusted replica/copy of the delayed incominganalogue signals (generated using one or both of the signal processingpaths within the second component 24). This combination of techniquescancels out a large proportion, if not all, of the noise and reduces theinterference to a much lower (acceptable) level. In addition, it is alsoenvisioned that in one embodiment, implementation of the signalreplication technique may involve first mixing the inverted and adjustedreplica analogue noise signals generated using the second signalprocessing path, followed by mixing inverted tonal signals generatedusing the first signal processing path. It will be appreciated that theorder in which the noise removal counter-measure techniques are appliedmay be governed by a set of logic rules that are stored by the first 22and/or second 24 component in the noise reduction system 20.

By eliminating the surrounding signals and background noise currentlypresent in the existing circuitry, the existing analogue signalprocessing circuitry 4 of the mobile phone will be able to amplify thewanted signal sufficiently to enable demodulation to occur withouterrors. The removal of errors will enable the system bandwidth to beentirely utilised for the transfer of data, without wasting anybandwidth on resending or correcting data decoded with errors.

FIGS. 8A to 8C highlight the beneficial effects that the noise reductionsystem described herein can have on existing signals.

FIG. 8A shows the frequency spectrum 200 of an example wanted signal inthe scenario where an adjacent interfering signal 205 is also present inthe selected passband. As previously mentioned, there is a need toincrease the SNR of the digital signal that is to be decoded, so as toensure that the SNR is sufficiently high to allow decoding of thedigital information contained within the signal. However, the presenceof the unwanted (interfering) noise signal 205 will result in areduction in amplification of the wanted signal 200, so as to preventthe amplified unwanted signal from exceeding the system's capabilities.The wanted signal 200 will therefore suffer significant degradation dueto the presence of the adjacent noise signals 205, and therefore theresultant decoding (bit rate) errors will be much greater. This can bevisualised in the constellation diagram of FIG. 8B, in which a largescatter in each of the four groups of points 210 in the diagram,corresponding to high bit rate errors, can be seen.

By contrast, FIG. 8C shows a constellation diagram of the bit rateerrors when decoding the same signal that was shown in FIG. 8A after ithas been acted upon by the noise reduction system 20 described herein.As can be clearly seen, the extent of scatter is greatly decreased, andthe points in each of the four groups 215 are grouped together much moredensely—it can therefore be ascertained (for example via measurements)that the bit rate errors have been significantly reduced.

Specifically, the decrease in bit rate errors indicated in FIG. 8C wasachieved by the applicant during a set of real-world tests using thenoise reduction system 20 described herein, which improved the recoveredsignal strength by 54 dBM. Other tests performed on real mobile 4G TLEsignals produced a 63 dBM improvement in the received signal. Therefore,as bit rate errors reduce proportionally to received signal increases,improved signal strengths will be perceived by the mobile phonereceivers, and the mobile network will be able to provide higher datarate transfers, as bandwidth will not be used up resending or correctingdata decoded with errors.

Many other advantages are also achieved via the use of the present noisereduction system 20. For example, power to the RF sections of a mobilephone can be reduced as the received signal strength is sufficient,thereby extending the overall battery life of the mobile phone.Furthermore, fewer cell towers will be required to cover a given area.

Many modifications may be made to the above examples without departingfrom the scope of the present invention as defined in the accompanyingclaims. In particular, it will be appreciated that the techniquesdescribed herein could be applied in all of the existing mobile networkstandards. For example, in mobile networks, such techniques would becompliant with current 3G and 4G standards, as well as proposed 5Gstandards.

Furthermore, as was previously discussed, the applications of thepresent noise reduction system 20 are diverse, and are not limited tomobile phones or other similar devices. For example, use of the presentnoise reduction system 20 recovers the signal losses down a given cableor fibre for broadband cable connections, and can thereby result in theextension of broadband signals. Similarly, Wi-Fi signal coverage canalso be significantly extended through use of the noise reductionsystem. Space (satellite-based) communications can also be achieved overlarger distances, or at a reduced power.

The invention claimed is:
 1. A noise reduction system for reducing noisein signals received at a digital receiver, the digital receivercomprising a digital receiver input for receiving an analogue signal,analogue signal processing circuitry for processing an analogue signal,and an output for providing the processed signal to a digital signalprocessor, wherein: the noise reduction system is located between thedigital receiver input and the analogue signal processing circuitry, andcomprises: a first component comprising: an input arranged to receivethe analogue signal from the digital receiver input; a processorarranged to assess the received analogue signal and to identify one ormore noise signals within the received analogue signal, wherein theprocessor of the first component is configured to convert the receivedanalogue signal into a digital signal, and to perform a mathematicaltransformation on the converted digital signal, the mathematicaltransformation identifying the one or more noise signals and at leastone property associated with each identified noise signal; and an outputarranged to output the results of the noise signal identification; and asecond component comprising: an input arranged to receive the results ofthe noise signal identification from the first component; and electroniccircuitry arranged, in dependence on the results of the noise signalidentification, to apply one or more counter-measures to the receivedanalogue signal to produce a modified analogue signal output to theanalogue signal processing circuitry, the modified analogue signalhaving a reduced level of noise compared to the received analoguesignal; wherein the noise reduction system is arranged to assess themodified analogue signal to identify sources of noise still presentwithin the analogue signal to determine whether any furthercounter-measures are required.
 2. The noise reduction system of claim 1,wherein the output of the first component is arranged to output theresults of the mathematical transformation to the second component. 3.The noise reduction system of claim 1, wherein the processor of thefirst component is configured to generate a digital matrix based on theresults of the mathematical transformation.
 4. The noise reductionsystem of claim 1, wherein the mathematical transformation comprises aFast Fourier Transform.
 5. The noise reduction system of claim 1,wherein the at least one property associated with each identified noisesignal is selected from the following group: central frequency of thesignal, signal amplitude, signal width, and signal modulation.
 6. Thenoise reduction system of claim 1, wherein the processor of the firstcomponent is arranged to extract each of the one or more identifiednoise signals from the incoming analogue signal, and the output of thefirst component is arranged to output the extracted analogue noisesignals to the second component.
 7. The noise reduction system of claim1, wherein one of the counter-measures applied by the electroniccircuitry of the second component comprises configuring and applying afilter to the incoming analogue signal to remove one of the identifiednoise signals.
 8. The noise reduction system of claim 7, wherein theprocessor of the first component is configured to convert the receivedanalogue signal into a digital signal, and to perform a mathematicaltransformation on the converted digital signal, the mathematicaltransformation identifying the one or more noise signals and at leastone property associated with each identified noise signal and whereinthe filter is configured using the at least one property associated withthe identified noise signal.
 9. The noise reduction system of claim 1,wherein the electronic circuitry of the second component is configuredto generate a replica noise signal corresponding to one of theidentified noise signals, to adjust the replica noise signal so that itis substantially in anti-phase with the identified noise signal and tomix the adjusted replica noise signal with the incoming analogue signalto produce the modified analogue signal.
 10. The noise reduction systemof claim 9, wherein the replica noise signal is generated based on thegeneration of a tonal signal.
 11. The noise reduction system of claim 9,wherein the processor of the first component is arranged to extract eachof the one or more identified noise signals from the incoming analoguesignal, and the output of the first component is arranged to output theextracted analogue noise signals to the second component and wherein thereplica noise signal is generated based on the extracted noise signalsreceived from the output of the first component.
 12. The noise reductionsystem of claim 1, wherein the processor of the first component isarranged to output a control signal to the second component to controlthe counter-measures that are applied by the electronic circuitry secondcomponent.
 13. The noise reduction system of claim 1, wherein theprocessor of the first component is arranged to assess the effectivenessof the one or more counter-measures applied by the second component. 14.The noise reduction system of claim 1, comprising a third component andwherein the output of the first component is arranged to output acontrol signal to the third component to assess the modified analoguesignal to identify sources of noise still present within the analoguesignal to determine whether any further counter-measures are required.15. The noise reduction system of claim 1, wherein at least one of thefirst and second components is arranged to be controlled via output of acontrol signal from the digital signal processor to the respectivecomponent.
 16. The noise reduction system of claim 14, wherein the thirdcomponent is arranged to be controlled via output of a control signalfrom the digital signal processor to the respective component.
 17. Thenoise reduction system of claim 1, wherein the input of the firstcomponent is arranged to receive the analogue signal from a mobiledevice aerial.
 18. The noise reduction system of claim 1, wherein theincoming analogue signal comprises any one of the following: mobilenetwork signals, radio signals, Wi-Fi signals, satellite communications,broadband connections.
 19. A noise reduction method for reducing noisein signals received at a digital receiver, the digital receivercomprising a digital receiver input for receiving an analogue signal,analogue signal processing circuitry for processing the analogue signal,and an output for providing the processed analogue signal to a digitalsignal processor, wherein the method comprises: assessing, by aprocessor of a first component located between the digital receiverinput and the analogue signal processing circuitry, the receivedanalogue signal received from the digital receiver input and identifyingone or more noise signals within the analogue signal, wherein theprocessor of the first component converts the received analogue signalinto a digital signal, and performs a mathematical transformation on theconverted digital signal, the mathematical transformation identifyingthe one or more noise signals and at least one property associated witheach identified noise signal; applying, by electronic circuitry of asecond component located between the digital receiver input and theanalogue signal processing circuitry, one or more counter-measures tothe received analogue signal in dependence on the identified noisesignals in order to produce a modified analogue signal output to theanalogue signal processing circuitry, the modified analogue signalhaving a reduced level of noise compared to the received analoguesignal; and assessing the modified analogue signal to identify sourcesof noise still present within the modified analogue signal to determinewhether any further counter-measures are required.
 20. A non-transitorycomputer-readable storage medium comprising computer programinstructions which, when executed by a computer, cause the computer tocarry out the operations of method of claim
 19. 21. A mobile devicecomprising the noise reduction system of claim
 1. 22. A WiFi routercomprising the noise reduction system of claim
 1. 23. The noisereduction method of claim 19, wherein the first component outputs theresults of the mathematical transformation to the second component. 24.The noise reduction method of claim 19, wherein the processor of thefirst component generates a digital matrix based on the results of themathematical transformation.
 25. The noise reduction method of claim 19,wherein the mathematical transformation comprises a Fast FourierTransform.
 26. The noise reduction method of claim 19, wherein the atleast one property associated with each identified noise signal isselected from the following group: central frequency of the signal,signal amplitude, signal width, and signal modulation.
 27. The noisereduction method of claim 19, wherein the processor of the firstcomponent extracts each of the one or more identified noise signals fromthe incoming analogue signal, and the first component outputs theextracted analogue noise signals to the second component.
 28. The noisereduction method of claim 19, wherein one of the counter-measuresapplied by the electronic circuitry of the second component comprisesconfiguring and applying a filter to the incoming analogue signal toremove one of the identified noise signals.
 29. The noise reductionmethod of claim 28, wherein the processor of the first componentconverts the received analogue signal into a digital signal, andperforms a mathematical transformation on the converted digital signal,the mathematical transformation identifying the one or more noisesignals and at least one property associated with each identified noisesignal and wherein the filter is configured using the at least oneproperty associated with the identified noise signal.
 30. The noisereduction method of claim 19, wherein the electronic circuitry of thesecond component generates a replica noise signal corresponding to oneof the identified noise signals, to adjust the replica noise signal sothat it is substantially in anti-phase with the identified noise signaland mixes the adjusted replica noise signal with the incoming analoguesignal to produce the modified analogue signal.
 31. The noise reductionmethod of claim 30, wherein the replica noise signal is generated basedon the generation of a tonal signal.
 32. The noise reduction method ofclaim 30, wherein the processor of the first component extracts each ofthe one or more identified noise signals from the incoming analoguesignal, and the first component outputs the extracted analogue noisesignals to the second component and wherein the replica noise signal isgenerated based on the extracted noise signals received from the outputof the first component.
 33. The noise reduction method of claim 19,wherein the processor of the first component outputs a control signal tothe second component to control the counter-measures that are applied bythe electronic circuitry second component.
 34. The noise reductionmethod of claim 19, wherein the processor of the first componentassesses the effectiveness of the one or more counter-measures appliedby the second component.
 35. The noise reduction method of claim 19,comprising a third component and wherein the first component outputs acontrol signal to the third component to assess the modified analoguesignal to identify sources of noise still present within the analoguesignal to determine whether any further counter-measures are required.36. The noise reduction method of claim 19, wherein at least one of thefirst and second components is arranged to be controlled via output of acontrol signal from the digital signal processor to the respectivecomponent.
 37. The noise reduction method of claim 35, comprisingcontrolling the third component via output of a control signal from thedigital signal processor to the respective component.
 38. The noisereduction method of claim 19, wherein the input of the first componentreceives the analogue signal from a mobile device aerial.
 39. The noisereduction method of claim 19, wherein the incoming analogue signalcomprises any one of the following: mobile network signals, radiosignals, Wi-Fi signals, satellite communications, broadband connections.40. A noise reduction system for reducing noise in signals received at adigital receiver, the digital receiver comprising a digital receiverinput for receiving an analogue signal, analogue signal processingcircuitry for processing an analogue signal, and an output for providingthe processed signal to a digital signal processor, wherein: the noisereduction system is located between the digital receiver input and theanalogue signal processing circuitry, and comprises: a first componentcomprising: an input arranged to receive the analogue signal from thedigital receiver input; a processor arranged to assess the receivedanalogue signal and to identify one or more noise signals within thereceived analogue signal; and an output arranged to output the resultsof the noise signal identification; and a second component comprising:an input arranged to receive the results of the noise signalidentification from the first component; and electronic circuitryarranged, in dependence on the results of the noise signalidentification, to apply one or more counter-measures to the receivedanalogue signal to produce a modified analogue signal output to theanalogue signal processing circuitry, the modified analogue signalhaving a reduced level of noise compared to the received analoguesignal, wherein one of the counter-measures applied by the electroniccircuitry of the second component comprises configuring and applying afilter to the incoming analogue signal to remove one of the identifiednoise signals; wherein the noise reduction system is arranged to assessthe modified analogue signal to identify sources of noise still presentwithin the analogue signal to determine whether any furthercounter-measures are required.
 41. The noise reduction system of claim40, wherein the processor of the first component is configured toconvert the received analogue signal into a digital signal, and toperform a mathematical transformation on the converted digital signal,the mathematical transformation identifying the one or more noisesignals and at least one property associated with each identified noisesignal.
 42. The noise reduction system of claim 41, wherein the outputof the first component is arranged to output the results of themathematical transformation to the second component.
 43. The noisereduction system of claim 41, wherein the processor of the firstcomponent is configured to generate a digital matrix based on theresults of the mathematical transformation.
 44. The noise reductionsystem of claim 41, wherein the mathematical transformation comprises aFast Fourier Transform.
 45. The noise reduction system of claim 41,wherein the at least one property associated with each identified noisesignal is selected from the following group: central frequency of thesignal, signal amplitude, signal width, and signal modulation.
 46. Thenoise reduction system of claim 40, wherein the processor of the firstcomponent is arranged to extract each of the one or more identifiednoise signals from the incoming analogue signal, and the output of thefirst component is arranged to output the extracted analogue noisesignals to the second component.
 47. The noise reduction system of claim40, wherein the processor of the first component is configured toconvert the received analogue signal into a digital signal, and toperform a mathematical transformation on the converted digital signal,the mathematical transformation identifying the one or more noisesignals and at least one property associated with each identified noisesignal and wherein the filter is configured using the at least oneproperty associated with the identified noise signal.
 48. The noisereduction system of claim 40, wherein the electronic circuitry of thesecond component is configured to generate a replica noise signalcorresponding to one of the identified noise signals, to adjust thereplica noise signal so that it is substantially in anti-phase with theidentified noise signal and to mix the adjusted replica noise signalwith the incoming analogue signal to produce the modified analoguesignal.
 49. The noise reduction system of claim 48, wherein the replicanoise signal is generated based on the generation of a tonal signal. 50.The noise reduction system of claim 48, wherein the processor of thefirst component is arranged to extract each of the one or moreidentified noise signals from the incoming analogue signal, and theoutput of the first component is arranged to output the extractedanalogue noise signals to the second component and wherein the replicanoise signal is generated based on the extracted noise signals receivedfrom the output of the first component.
 51. The noise reduction systemof claim 40, wherein the processor of the first component is arranged tooutput a control signal to the second component to control thecounter-measures that are applied by the electronic circuitry secondcomponent.
 52. The noise reduction system of claim 40, wherein theprocessor of the first component is arranged to assess the effectivenessof the one or more counter-measures applied by the second component. 53.The noise reduction system of claim 40, comprising a third component andwherein the output of the first component is arranged to output acontrol signal to the third component to assess the modified analoguesignal to identify sources of noise still present within the analoguesignal to determine whether any further counter-measures are required.54. The noise reduction system of claim 40 wherein at least one of thefirst and second components is arranged to be controlled via output of acontrol signal from the digital signal processor to the respectivecomponent.
 55. The noise reduction system of claim 53, wherein the thirdcomponent is arranged to be controlled via output of a control signalfrom the digital signal processor to the respective component.
 56. Thenoise reduction system of claim 40, wherein the input of the firstcomponent is arranged to receive the analogue signal from a mobiledevice aerial.
 57. The noise reduction system of claim 40, wherein theincoming analogue signal comprises any one of the following: mobilenetwork signals, radio signals, Wi-Fi signals, satellite communications,broadband connections.
 58. A noise reduction method for reducing noisein signals received at a digital receiver, the digital receivercomprising a digital receiver input for receiving an analogue signal,analogue signal processing circuitry for processing the analogue signal,and an output for providing the processed analogue signal to a digitalsignal processor, wherein the method comprises: assessing, by aprocessor of a first component located between the digital receiverinput and the analogue signal processing circuitry, the receivedanalogue signal received from the digital receiver input and identifyingone or more noise signals within the analogue signal; applying, byelectronic circuitry of a second component located between the digitalreceiver input and the analogue signal processing circuitry, one or morecounter-measures to the received analogue signal in dependence on theidentified noise signals in order to produce a modified analogue signaloutput to the analogue signal processing circuitry, the modifiedanalogue signal having a reduced level of noise compared to the receivedanalogue signal, wherein one of the counter-measures applied by theelectronic circuitry of the second component comprises configuring andapplying a filter to the incoming analogue signal to remove one of theidentified noise signals; and assessing the modified analogue signal toidentify sources of noise still present within the modified analoguesignal to determine whether any further counter-measures are required.59. The noise reduction method of claim 58, wherein the processor of thefirst component converts the received analogue signal into a digitalsignal, and performs a mathematical transformation on the converteddigital signal, the mathematical transformation identifying the one ormore noise signals and at least one property associated with eachidentified noise signal.
 60. The noise reduction method of claim 59,wherein first component outputs the results of the mathematicaltransformation to the second component.
 61. The noise reduction methodof claim 59, wherein the processor of the first component generates adigital matrix based on the results of the mathematical transformation.62. The noise reduction method of claim 59, wherein the mathematicaltransformation comprises a Fast Fourier Transform.
 63. The noisereduction method of claim 59, wherein the at least one propertyassociated with each identified noise signal is selected from thefollowing group: central frequency of the signal, signal amplitude,signal width, and signal modulation.
 64. The noise reduction method ofclaim 58, wherein the processor of the first component extracts each ofthe one or more identified noise signals from the incoming analoguesignal, and the first component outputs the extracted analogue noisesignals to the second component.
 65. The noise reduction method of claim58, wherein the processor of the first component converts the receivedanalogue signal into a digital signal, and performs a mathematicaltransformation on the converted digital signal, the mathematicaltransformation identifying the one or more noise signals and at leastone property associated with each identified noise signal and whereinthe filter is configured using the at least one property associated withthe identified noise signal.
 66. The noise reduction method of claim 58,wherein the electronic circuitry of the second component generates areplica noise signal corresponding to one of the identified noisesignals, to adjust the replica noise signal so that it is substantiallyin anti-phase with the identified noise signal and mixes the adjustedreplica noise signal with the incoming analogue signal to produce themodified analogue signal.
 67. The noise reduction method of claim 66,wherein the replica noise signal is generated based on the generation ofa tonal signal.
 68. The noise reduction method of claim 66, wherein theprocessor of the first component extracts each of the one or moreidentified noise signals from the incoming analogue signal, and thefirst component outputs the extracted analogue noise signals to thesecond component and wherein the replica noise signal is generated basedon the extracted noise signals received from the output of the firstcomponent.
 69. The noise reduction method of claim 58, wherein theprocessor of the first component outputs a control signal to the secondcomponent to control the counter-measures that are applied by theelectronic circuitry second component.
 70. The noise reduction method ofclaim 58, wherein the processor of the first component assesses theeffectiveness of the one or more counter-measures applied by the secondcomponent.
 71. The noise reduction method of claim 58, comprising athird component and wherein the first component outputs a control signalto the third component to assess the modified analogue signal toidentify sources of noise still present within the analogue signal todetermine whether any further counter-measures are required.
 72. Thenoise reduction method of claim 58, wherein at least one of the firstand second components is arranged to be controlled via output of acontrol signal from the digital signal processor to the respectivecomponent.
 73. The noise reduction method of claim 71, comprisingcontrolling the third component is via output of a control signal fromthe digital signal processor to the respective component.
 74. The noisereduction method of claim 58, wherein the input of the first componentreceives the analogue signal from a mobile device aerial.
 75. The noisereduction method of claim 58, wherein the incoming analogue signalcomprises any one of the following: mobile network signals, radiosignals, Wi-Fi signals, satellite communications, broadband connections.76. A non-transitory computer-readable storage medium comprisingcomputer program instructions which, when executed by a computer, causethe computer to carry out the operations of method of claim
 58. 77. Amobile device comprising the noise reduction system of claim
 40. 78. AWiFi router comprising the noise reduction system of claim 40.